The present invention relates to a disk brake and a disk brake for a railway vehicle.
A floating caliper type disk brake that prevents a drag phenomenon of a brake pad has been known (refer to Patent Document 1).
This floating caliper type disk brake is configured such that one of pads (brake pads) is fixed to an arm at one end of a caliper (floating caliper) where both end portions are open in a bifurcated manner and the other pad is pushed out toward a rotor by a piston (driving piston) disposed on an arm on the side opposite to the arm. Two guide pins are fixed to the arm at the other end of the caliper, and these guide pins are supported to be capable of sliding in an axial direction by a tubular portion of a support coupled with a bogie frame or the like.
In other words, as illustrated in FIG. 13A, a pair of upper and lower guide pins 503 (only that on an upper side being illustrated herein) are laid across a pair of bifurcated arms 501 of the caliper and are fixed to the arms 501 by a flange 505 and a nut (not illustrated), respectively. A pair of holding rings 509 are mounted, pinched by stepped portions 511 and snap rings (not illustrated), on an inner surface of a tubular portion 507 of the support (not illustrated) surrounding the guide pin 503 on the upper side. Retraction rubber rings (friction rubber rings) 513 that have an H-shaped cross-sectional shape are mounted inside the holding rings 509.
In the above-described configuration, tip portions of projections 515 in inner peripheries of the retraction rubber rings 513 that have the H-shaped cross-sectional shape directly abut against an outer peripheral surface of the guide pin 503, as illustrated in FIG. 13A, during non-braking.
When braking is performed, a reaction force by which the pad is pressed against the rotor causes the guide pin 503 to be moved along with the caliper in the direction of arrow A that is illustrated in FIG. 13B. In addition, friction between the outer peripheral surface of the guide pin 503 and the tip portions of the projections 515 causes the projections 515 of the retraction rubber rings 513 to be bent (twisted) in the direction of arrow A.
When the braking is released, the retraction rubber rings 513 return to original postures based on resilience thereof, and the guide pin 503 is moved in the direction of arrow B that is illustrated in FIG. 13C due to friction between the tip portions of the projections 515 in the inner peripheries and the outer peripheral surface of the guide pin 503. Then, the caliper that is coupled with the guide pin 503 is slightly moved in the direction of arrow B, so that the pad fixed to the caliper is slightly separated from the rotor. Then, a vehicle can be started in a light manner. When the vehicle begins to travel, a gap between the pad and the rotor sufficiently increases because of vibration or the like.
According to this floating caliper type disk brake, the pad fixed to the caliper is pulled apart from the rotor by the retraction rubber ring 513 immediately after the release of the braking. Accordingly, drag can be prevented, an increase in starting torque can be prevented, and lining wear can be prevented.
[Patent Document 1] JP-UM-A-6-32773